Knives have long been used for many purposes in various environments, such as paring knives used in home kitchens, butcher knives and cleavers used in butcher shops, multi-tool or utility knives used as box cutters in warehouses, survival knives used by outdoorsmen and having a hollow handle for storing equipment, surgical knives used in surgical procedures, special purpose knives (e.g., plastic, wood and ceramic) to avoid detection by metal sensing equipment, and many other types and sizes of knives for a multiplicity of uses.
In any of the environments mentioned hereinabove, it is important that knives be maintained in a sharpened state. The terminology “sharpen”, “sharpened”, “sharpening” and variants thereof is defined herein to mean the process of regrinding a knife blade edge or the state of having a reground knife blade edge, preferably ground to the blade edge's original angle, if known. It is important to maintain knives in a sharpened state because a dull knife is more difficult to control when being used and, therefore, may slip and injure the user. In this regard, a user will apply more pressure to compensate for the dullness of the knife. Application of more pressure can lead to loss of control of the knife that, in turn, can lead to injury. Also, a dull knife requires more effort on the part of the user because a dull knife requires more pressure to cut an item. In this case, repeated cutting with a dull knife will be more tiring for the user compared to cutting with a sharp knife. In addition, a dull knife can leave a jagged edge on the item being cut. In the case of food preparation, the jagged edge can cause uneven cuts when the user is attempting to make thin cuts. Using dull knives may even present a health risk when cutting food, such as raw fish items (e.g., sushi and shell fish), oysters, clams and mussels. For example, shell fish can carry vibrio bacteria that can lead to “vibrio-cholerae”, which is a cholera-related, gastrointestinal illness. Such a cholera-related, gastrointestinal illness can present a serious health risk to persons having immune-deficiency health issues. More specifically, the uneven edge of a dull knife blade will leave a jagged edge in the fish item being cut. Such a jagged edge is more prone to collect populations of bacteria thereat. Ingestion of the raw fish containing the bacteria can increase the afore-mentioned health risk.
Therefore, it is important that the cutting edge of a knife be sharp to avoid risk of injury, unnecessary exertion, and risks to human health. It is also important that, once sharpened, the knives be maintained in a sharpened condition.
However, as known by persons of ordinary skill in the art of abrading devices, maintaining knives in a sharpened condition has proven to be challenging. For example, soft stainless steel knives, which are found in many retail stores, are difficult to sharpen. Hence, soft stainless steel knives are more difficult to maintain in a sharpened state. Also, some knives when washed in a dishwasher using dishwashing soap or detergent can develop a dull cutting edge over time, unless periodically resharpened. Also, leaving a knife in a pan of soapy water can develop a dull cutting edge over time, unless periodically resharpened. Loose storage of the knife, such as being loosely stored in a drawer and having the blade portion exposed rather than being individually separated and sheathed, can cause impact damage to the knife blade. Impact damage to the knife blade can also create a dull cutting edge over time, unless periodically resharpened.
Another challenge to suitably sharpening knives is knives are manufactured in widely varying styles, sizes, shapes, blade materials, blade hardness, blade contour, and blade facet angle. For example, with regard to blade angle, knives are typically manufactured having at least one of two well-known blade angles. More specifically, Euro-American style blades typically have a manufactured included V-shaped blade angle of 20° in transverse cross-section. Asian style knives, on the other hand, have a manufactured included V-shaped blade angle of between about 12° and about 15° in transverse cross-section. Therefore, a user having both Euro-American style knives and Asian style knives may find it necessary to purchase two types of knife sharpeners to properly sharpen both styles of knives. This could be inconvenient and financially prohibitive for some users.
Approaches have been proposed for addressing the challenges mentioned hereinabove. For example, U.S. Pat. No. 4,494,339 to Pittaway relates to knife sharpeners of a kind which are incorporated in a holder for the knife in which the knife is placed when not in use. The knife sharpener comprises the holder for the knife when the knife is not in use, sharpening means (i.e., an abrasive wheel) for sharpening the cutting edge of the knife as a result of the action of positioning the knife in the holder and/or the action of withdrawing the knife from the holder. Means are provided for selectively varying the pressure of engagement of the cutting edge with the sharpening means to vary the extent of sharpening occurring during withdrawal and/or replacement of the knife. Means are also provided for removing any particles which may adhere to the knife as a result of the sharpening action. More specifically, an optional feature is the provision of means for cleaning particles from the knife during insertion and/or withdrawal of the blade from the holder and may take the form of a pair of brushes, magnets provided in a removable frame, or magnetized particles in a plastic molding which constitutes the frame of the device.
Another approach is provided by U.S. Pat. No. 5,390,431 to Friel. This patent relates to an improved method and apparatus for sharpening knives and blades. According to this patent, a multi-stage process is used to sharpen knives and blades. More specifically, both facets of a double faceted blade are simultaneously sharpened as the facets are moved across a first pair of planar abrasive coated surfaces in a first stage. The abrasive coated surfaces cross to form a vertex. The abrasive coated surfaces are also positioned to establish a total included angle at the vertex nominally equal to the intended total included angle of the edge facet. A second stage sharpens closer to the edge of the blade and in general a finer grit abrasive will be used in the second stage to refine and perfect the edge geometry. This patent states that, where there would be excessive wear over extended periods of time, provisions in the sharpener's design can be made for the rapid replacement of the abrasive surfaces. This patent also states that where ferromagnetic knives are sharpened, the invention may be practiced by providing a magnet in the sharpening section to collect the metal filings.
Yet another approach is provided by U.S. Patent Application Publication US2009/0233530 to Friel, Sr, et al. This published patent application relates to a precise knife sharpener that is versatile in that it can sharpen virtually all of a large variety of knives made throughout the world, with widely different edge angles, to create edges of original factory quality. This patent application publication recognizes that knives from Asia are generally sharpened at very low edge angles with a primary edge facet centered at about 15°. This patent application publication also recognizes that knives of European, American or Western countries generally are sharpened at higher angles of about 20° for the primary facet. According to this patent, the apparatus of the invention is flexible enough to sharpen both 15° and 20° knives and yet create better than factory quality edges on both, The motor driven sharpener of the invention has two sharpening stages. These stages are Stage 1, Stage 2 and a single stropping Stage 3. Stage 1 is designed for and dedicated to the initial sharpening of Asian style knives that have 15 degree primary facets and which are inserted alternatively in a left and then in a right slot of the first stage. Euro-American style knives are sharpened in Stage 2 where knife guides are set at an angle of about 20°. At Stage 3, knife guides are set at a large angle to the vertical, compared to Stage 1. All knives, after their initial sharpening in Stage 1 or Stage 2, are finished by stropping in Stage 3.
Although the approaches recited hereinabove disclose various means for abrasively sharpening knives, the approaches recited hereinabove do not appear to disclose the invention described and claimed hereinbelow.